Right on Target: Elon Extended Depth of Focus IOL

While multifocal IOLs create two or three distinct focal points, EDOF lenses provide a single elongated focal range to enhance the depth of focus. For a real EDOF lens, concentrating the light into a narrow channel produces good vision over an extended range of distances. The width of the channel defines how sharp the images are, while the length of the channel determines the range of distances where the EDOF operates. If the EDOF channel is too wide, the non-concentrated light may cause blur, halos, glare, and deteriorate visual quality. EDOF technologies aim to collect the maximum amount of light into the channel to provide high visual performance and reduce the amount of undesirable photic phenomena.

Simulated polychromatic through-focus point spread functions simulating the generation of elongated focus,
by modifying the steepness of the linking zones.

The Wavefront Linking technology created by Medicontur generates an elongated focus by using carefully chosen wavefront-forming elements. The concept is based on the operation of a conventional refractive multifocal intraocular lens, which has been further modified to achieve an extended depth of focus. When refractive zones with different radii and curvatures are connected, each contributes to a discrete focal point. With carefully engineered smooth transitions, the light energy distribution becomes continuous along the optical axis. Wavefront Linking bridges the focal points and generates an elongated focus from far to intermediate distances with functional near vision,¹ the latter being unexpected for an EDOF IOL. The refractive zones of Elon are connected by 20 µm wide linking zones.

The Elon intraocular lens is a single-piece IOL manufactured from a high-quality hydrophobic acrylic material, including a UV filter and a mild blue light filter.² For a short deep dive into IOL materials, here we have an excellent material with an exceptionally high Abbe number of 58 (the highest available in the market), producing low chromatic aberrations (low level of dispersion of light). The refractive index is low, negating the effect of reflections off the IOL, which some patients report after cataract surgery. In addition the glass transition temperature (Tg) is low, meaning the IOL unfolds easily and optimally in the operating theatre, unlike very slow unfolding IOLs where the material Tg is too high. The Elon is available in non-toric (877PEY), and toric (877PETY) models for the correction of corneal astigmatism. The overall diameter of the IOL is 13.0 mm with a 6.0 mm wide biconvex aspheric optic.^3,4

The Bi-Flex design of the IOL consists of fenestrated double C-loop haptics with 0° angulation, providing very good long-term refractive outcomes and excellent rotational stability. The large contact angle between the IOL and the equator of the capsular bag contributes to stable results in the long term.^5,6 A 360° square edge helps reduce the occurrence of posterior chamber opacification (PCO).^3,4

Elon is available in a wide range of IOL powers, enabling tailor-made solutions for all patients. Bi-Flex Elon POB-MA (877PEY) IOL is available from +8.00 D to +35.0 D (0.50 D increments), and Bi-Flex Elon Toric POB-MA (877PETY) is available from +10.0 D to +35.0 D (0.50 D increments) with cylinder dioptre powers of +1.00 D – +6.00 D.⁷ The Elon IOL is available as part of the POB-MA preloaded injector system.^3,4

POB-MA preloaded injector system.

Clinical Outcomes and Patient Satisfaction

I recently performed a retrospective pilot evaluation of 50 eyes (25 patients), focussing on the safety and performance of binocular implantation of Elon (877PEY) and Elon Toric (877PETY) lenses. The goal was to restore intermediate and distance vision, and simultaneously correct preoperative corneal astigmatism in cataract patients. Refractive outcomes, monocular and binocular uncorrected and corrected distance (UDVA, CDVA), intermediate (UIVA, DCIVA), and near (UNVA, DCNVA) visual acuities were measured during a three-month follow-up period. Monocular distance-corrected visual acuity defocus curves (VADC) and contrast sensitivity defocus curves (CSDC) were also plotted. Patient satisfaction was assessed according to Catquest⁸ and the Patient-Reported Spectacle Independence Questionnaire (PRISQ).⁹ Here I discuss the results of the initial 88% of the target trial enrolment.

The Medicontur Elon lens family provided accurate and predictable correction of refraction. The postoperative spherical equivalent refraction was within 0.5D of target in 100% of cases. The postoperative cylinder was within 0.5D of target in 93% of cases.

Elon provided excellent distance visual acuity results with UDVA of 6/6 or better found in 76% of cases and 6/7.5 or better in 93% of cases. Intermediate vision distance corrected was N10 or better in 77% of cases and N12 or better in 100% of cases. Near vision performance was surprisingly better than that expected from an EDOF lens, and these results were also supported by the patient-reported outcomes measured by the questionnaires.

Elon offers an extended depth of focus across a wide defocus range, maintaining visual acuity above 0.2 logMAR. These IOLs meet the criteria defined by a newly published, evidence-based functional classification system, which considers the endpoints described in standards,¹⁰ particularly the Range of Field (RoF) measured through monofocal visual acuity defocus curves with the best distance correction.¹⁴ This categorisation, based on functional outcomes, is designed to complement the existing technical IOL specifications, hence providing the scientific community with a clearer understanding of IOL performance. In doing so, it helps clinicians find the optimal IOL solution for each patient.¹¹

Binocular visual acuity defocus curve, three months postoperative.

The unique Wavefront Linking zone in the optic also ensures outstanding contrast sensitivity across the entire defocus range. According to patient-reported outcome measures, most patients experienced no or minimal difficulties with their daily activities and hardly any disturbing photic phenomena after Elon implantation.

When targeting emmetropia in both eyes, spectacle independence is usually achieved at far and intermediate distances, while activities requiring a high level of precision and focus at close range may still require additional low power correction, such as +1.0 readers. While trifocal IOLs are designed to offer spectacle-free vision across all distances, some patients experience issues with dysphotopsia. In contrast, EDoF IOLs are less likely to cause unwanted photic phenomena. Patients reported high-level visual comfort and general daily activities were performed without or with minimal difficulties.¹²

My clinical experience also confirmed that binocular implantation of Elon in a micro-monovision approach maximises the benefits of the extended focus. In micro-monovision, the dominant eye is targeted for emmetropia and the non-dominant eye for slight myopia, creating a different EDoF channel for each eye. The technique aims to enhance near vision without compromising far and intermediate vision, allowing patients to extend their spectacle independence.

Conclusions

Innovative Wavefront Linking technology used to design the Elon EDOF IOL enables the creation of a wide range of continuous vision, and its non-diffractive design greatly reduces the risk of visual disturbances. Elon is a safe and effective choice for patients of any age who lead active lifestyles and prioritise visual quality, even if glasses are occasionally needed for near tasks. This lens is also an ideal option for patients with borderline anatomical conditions or when the visual outcome with a trifocal IOL is uncertain or unpredictable. Additionally, the Elon toric version allows for the simultaneous treatment of presbyopia and preoperative corneal astigmatism. The patient reported outcome measures supported high levels of satisfaction.

Dr Alison Chiu FRANZCO  PhD MBBS (Hons)  BMedSc (Hons I) Grad Dip Refractive Surgery is fellowship-trained in laser vision correction and lens-based refractive surgery. Her expertise includes all forms of laser surgery, routine and complex cataract surgery, refractive lens exchange (clear lens exchange) surgery, and implantable collamer lens (ICL) surgery. Dr Chiu has a special interest in complex cataract surgery and is an expert in refractive vision correction. She has contributed to the success of over 40,000 laser vision corrections performed at one of Australia’s leading refractive surgical centres. She is based in Sydney’s CBD and western suburbs.

References

1. Extended Depth of Focus with the Bi-Flex Elon IOL. A supplement in the EuroTimes. September 2022. Available at: escrs.org/eurotimes-articles/supplement-extended-depth-of-focuswith-the-bi-flex-elon-iol.
2. Argay A, Vamosi P. The assessment of the impact of glistening on visual performance in relation to tear film quality. PLoS One. 2020;15(10):e0240440. doi: 10.1371/journal.pone.0240440.
3. Hydrophobic EDOF Preloaded datasheet.
4. Hydrophobic EDOF Toric Preloaded datasheet.
5. Novacek LV, Nemcova M, Rozsival P, et al. Evaluation of astigmatism-correcting efficiency and rotational stability after cataract surgery with a double-loop haptic toric intraocular lens: a 1-year follow-up. Biomed Hub. 2021;6(1):30-41.doi: 10.1159/000513894.
6. Bachernegg A, Ruckl T, Dexl AK, et al. Vector analysis, rotational stability, and visual outcome after implantation of a new aspheric toric IOL. J Refract Surg. 2015;31(8):513-20. doi: 10.1016/j.jcrs.2013.03.033.
7. Manufacturer: Medicontur Medical Engineering Ltd. Available at: medicontur.com. Accessed September 2024.
8. Lundstrom M, Roos P, Jensen S, Fregell G. Catquest questionnaire for use in cataract surgery care: description, validity, and reliability. J Cataract Refract Surg. 1997;23(8):1226-36. doi: 10.1016/s0886-3350(97)80321-5.
9. Alonso J, Espallargues M, Bernth-Petersen P, et al. International applicability of the VF-14. An index of visual function in patients with cataracts. Ophthalmology. 1997;104(5):799-807. doi: 10.1016/s0161-6420(97)30230-9.
10. ISO-11979-7:2024. Part 7: clinical investigations of intraocular lenses for the correction of aphakia. 2024. Available at: iso.org/standard/79689.html.
11. Fernandez J, Ribeiro F, Rocha-de-Lossada C, Rodriguez-Vallejo M. Functional classification of intraocular lenses based on defocus curves: a scoping review and cluster analysis. J Refract Surg. 2024;40(2):e108-e16. doi: 10.3928/1081597X-20231212-01.
12. Lee MW. Visual outcomes following implantation of a novel non-diffractive wavefront-linking extended depth of focus intraocular lens. 39th Asia-Pacific Academy of Ophthalmology; 2024 22–25 Feb 2024; Bali, Indonesia. doi: 10.1007/s10792-024-03247-x.